DE102011010330B4 - extrusion die - Google Patents

Abstract

Extrusion tool (40) for fanning at least one fiber strand (5) and for impregnating the fiber strand (5) with a polymer melt, wherein the extrusion tool comprises a fan body (41) and a fan body (41) surrounding the hood (56), wherein the hood a central opening (57) for the at least one fiber strand (5), wherein the at least one fiber strand (5) on the side of the fan body (41) for opening in the hood (56), fanning the at least one fiber strand (5) on the fan body (41) is guided, wherein the fan body (41) in the region of the fanning of the at least one fiber strand (5) has at least one outlet opening (49) for the polymer melt, characterized in that the fan body (41) provided with a hemispherical curvature head (42), wherein the head (42) has a neck (45), the neck (45) forming at least one opening (51) for at least a fiber strand (5) is connected to a carrier (46) and wherein the neck (45) in the region of the transition to the head (42) has the at least one outlet opening (49) for the polymer melt.

Description

The invention relates to an extrusion tool according to the preamble of claim 1.

The use of fiber-reinforced thermoplastic granules for the production of workpieces by injection molding is well known in the art. Such granules, also called compounds, are produced in so-called compounding processes. For the production of such compounds or granules fiber strands are used, which consist of a plurality of filaments.

The fiber or yarn strands may consist of the prior art, for example, from natural or cellulose fibers or glass fibers. From the EP 1 436 130 B1 In this context, a process for the production of granules for the production of plastic moldings is known, wherein continuous regenerated cellulose fibers are coated in a first step in a pultrusion process with a matrix material of a technical plastic, and a bonding agent, then granulated, and after a extruded again subsequent drying process and re-granulated and dried. That is, from this reference, a method is known in which one or more fiber strands on its circumference with a polymer, for. B. coated with propylene, this sheathed fiber strand is then processed in a first step to a granulate. The coating with the polymer melt takes place, depending on the polymer used at temperatures of well over 200 degrees Celsius. This means that even at this step, the fibers are exposed to significant temperatures. A fiber strand made in such a way is then cut into granules. It has been found that in the granulation process, ie when cutting the strand into individual sections, individual fibers are released from the composite, and protrude over the individual pieces of granules. This means that the fibers in the granules have a quite different length. In a further processing step, the cut granules are placed in an extruder. In the extruder, both under heat and under mechanical action, a mass is prepared which should have a uniform distribution of the fibers in the mixture. After extrusion and shaping into an extrusion strand, the strand is again granulated in a further step, in order then to be processed as a material, for example by injection molding, into corresponding workpieces.

It has been found, however, that the distribution of the fibers in the finished workpiece is uneven, d. H. It has been found that the workpiece has a plurality of so-called fiber esters. The reason for this is obviously to be found in the fact that although the granules produced in the first process step have a corresponding polymer layer on their circumference. However, the cladding with such a polymer does not cause penetration of the fiber strand in the sense that within the fiber strand, the polymer forms the matrix material for the filaments. This obviously does not change the processing of the granules in the extruder. That is, the granules according to the prior art has the disadvantage that the distribution of the fibers in the granules, which ultimately serves for the production of the workpiece is not evenly distributed, so that form individual fiber esters in the workpiece, the uneven strength of a cause it produced components. In addition, due to the taking place in two process steps heat supply on the one hand, a considerable energy demand, and secondly, depending on the polymer used and the associated melting temperature, especially in high-melting polymers such. As polyamide, when using cellulose fibers, the risk that these damage. Because cellulose fibers decompose depending on the height of the temperature and the duration of the temperature load.

From the DE 195 23 490 A1 It is known to spread the fiber strand by opposing rings and thus to open the fiber strand on the rings. The feeding of the melt takes place at a point between the impregnating jacket and the impregnating core, namely in the region of the outlet of the fiber strands from the inlet openings of the impregnating core into the intermediate space between the impregnating jacket and the impregnating core. The individual fiber strands are guided over the length of the impregnating core over a plurality of expansion rings, wherein a multiple spreading of the fiber strand takes place by the multiple and in pairs an opposing arrangement of expansion rings, but at the same time also a fanning out. This is to ensure that the polymer melt captures the individual fibers of the filaments of the fiber strands on all sides. By provided over the length of the impregnating core several deflections of the fiber strand a complete impregnation of the individual fibers of the fiber strand is to be ensured with the polymer melt. Due to the arrangement of a plurality of successively arranged deflection by the arrangement of a plurality of pairs arranged in succession spreader rings, however, the residence time of the fiber strand in the tool is substantially increased. In particular, when using cellulose fibers there is a risk that they will be damaged. Because the cellulose fibers will depend on the amount of temperature and in particular the duration of the temperature stress, decompose more or less quickly. That is, the device known from the prior art is not suitable for the use of cellulose fibers.

Also from the EP 364 828 A2 It is known to guide the individual fiber strands over a plurality of deflections during the impregnation process, resulting in extending over a long period of temperature stress result. That is, also the doctrine of EP 364 828 A2 is not suitable to impregnate cellulosic fibers with a polymer melt, since there is a risk that at the time of exit of the composite material from the extrusion die, the cellulose fibers have largely decomposed.

The object underlying the invention is therefore to provide an extrusion tool of the type mentioned, which allows the production of granules having a homogeneous distribution of the filaments in the polymer matrix; Furthermore, the temperature load during the manufacturing process should be kept low. For the following considerations, a fiber strand is defined as such having a plurality of filaments or fibers.

To achieve the object serve the features of the characterizing part of claim 1 in conjunction with the features of the preamble.

The extrusion tool for fanning out at least one fiber strand and for impregnating the fiber strand with a polymer melt, characterized by a fan body and a hood surrounding the fan body, wherein the hood has a central opening for the at least one fiber strand, the at least one fiber strand first side of the Fan body axially parallel to the fan body and then guided to the central opening in the hood with fanning the at least one fiber strand on the fan body, wherein the fan body has at least one outlet opening for the polymer melt in the fanning of the at least one fiber strand. By guiding the fiber strand on the fan body fanning or spreading of the fiber strand occurs with the result that the individual filaments more or less exposed, so that the polymer melt supplied in this region of the fan body to a homogeneous embedding of the individual filaments of a fiber strand in the polymer melt leads.

The fan body has a head provided with a curvature, in particular a hemispherical curvature. It has already been pointed out elsewhere that the fan body is surrounded by a hood spaced apart to form an annular space, this hood having a central opening. The hood surrounds the curvature of the fan body such that the central opening in the hood is aligned with the central longitudinal axis of the fan body, thus the central opening is aligned with the pole of the hemispherical curvature.

The head has a neck, the neck being connected to a support to form at least one opening for at least one fiber strand. From this it is clear that the fiber strand is first guided laterally on the fan body, is guided through the central opening in the hood of the fiber strand over the head, and in this case the fiber strand due to the lateral offset of the fiber strand, due to the leadership of the fiber strand side of the neck to the central opening in the hood, the fiber strand is fanned out. That is, the maximum width of the fan is at the line in the transition from neck to head.

Here, the neck in the region of the transition to the head, the at least one outlet opening for the polymer melt. This means that the polymer melt is already brought into contact with the individual filaments of the fiber strand during fan formation in the region of the neck, and in particular in the region of the neck to head transition.

According to a particular feature of the invention, it is provided in this connection that adjoins the outlet opening for the polymer melt a tangentially extending in the direction of the head groove. This gives the polymer melt a twist in the circumferential direction of the fan body, which contributes in particular to the fact that during the fanning of the fiber strand, the individual filaments are wetted from all sides with the polymer melt. In this context, it should be pointed out in particular that the hood surrounds the fan body at least as far as the region of the outlet openings for the polymer melt, forming a small radial distance.

For the supply of the melt is provided that the carrier has a radially extending into the fan body inlet opening, which communicates through a channel in the fan body with the at least one outlet opening for the polymer melt.

In particular, the carrier is formed as a ring carrier, which surrounds the fan body spaced to form one, but preferably a plurality of circumferentially distributed openings for a plurality of fiber strands, the neck circumferentially distributed in the region of the transition to the head identifies several outlet openings for the polymer melt. It follows that at the same time a plurality of fiber strands can be supplied to the extrusion tool in a continuous process, which are fanned and impregnated by the fan body, but then through the central opening in the hood together as a strand of several individual fiber strands from the extrusion die be led out. That is, the cross section of the central opening in the hood is largely determined by the number of fiber strands and the strength of the individual fiber strands. The impregnated strand emerging from the hood is called a prepreg strand.

The impregnation with the polymer melt of the at least one fiber strand continuously supplied to the extrusion tool in the fanned-out state ensures that the polymer melt can essentially be laid around each individual filament of a fiber strand, so that the completely impregnated fiber strand not only, as in the prior art the case is on his coat a layer of a polymer, but the polymer is homogeneously distributed within the fiber strand. That is, the polymer forms a matrix for the filaments in the fiber strand.

With reference to the drawings, the invention will be explained in more detail below by way of example.

1 shows schematically the individual process steps for the preparation of a compound;

2 shows in a side view in section schematically the extrusion die;

2a shows a perspective view of the fan body without hood;

3 shows a tempering device in the form of a pair of rollers in a side view;

3a shows a view along the line IIIa / IIIa 3 ;

4 schematically shows the process wherein cut fiber strand sections are fed directly to an extruder;

5 shows schematically the cutting tool;

6 schematically shows a cut fiber strand section;

7 schematically shows a deflection device, which may be connected downstream of the extrusion tool (1st embodiment) or the extruder (2nd embodiment).

The representation of the first method is based on the 1 , The one with 10 designated bobbin holder comprises six coils 11 , whereby from the six coils 11 one fiber strand each 5 withdrawn continuously and accordingly continuously supplied to the other processing stations of the process, so that one of the Granuliereinrichtung supplied endless-Prepregstrang arises. Each of these fiber strands 5 becomes a drying device 20 supplied by the drying device 20 the individual fiber strands 5 For example, by means of hot air or by means of radiant heaters are dried before acting as individual fiber strands 5 with the 40 designated extrusion tool to be supplied. The extrusion tool 40 includes the with 41 designated fan body and the with 56 designated hood. The hood 56 forms a distance to the fan body 41 , which creates an annulus 58 shows, as this also directly in view of 1 results. Furthermore, an extruder 30 provided a polymer melt in annulus 58 between hood and fan body 41 introduces. In the room 58 become the fiber strands 5 each introduced separately, being in the range of the arrow 40a a fanning of the individual fiber strands takes place, as has already been described above, and as is also the subject of the invention. Then the individual fiber strands become 5 through the centric opening 57 from the extrusion tool 40 led out. The individual fiber strands 5 in this case form an impregnated fiber strand, as a prepreg strand 55 referred to as. The prepreg strand 55 goes through a nozzle 60 , which serves the compaction and shaping of the impregnated fiber strand.

Then the prepreg strand becomes 55 a tempering device 70 supplied, which will be described in detail elsewhere. After passing through the tempering is a with 80 designated strip deduction provided, the granulator 90 is subordinate to the preparation of the compound granules.

Out 2 now results in the formation of the extrusion tool 40 , The extrusion tool 40 is composed, as has already been explained from the fan body 41 and the hood surrounding the fan body 56 , Between the hood 56 on the one hand and the fan body 41 On the other hand, there is a distance through which the annulus designated 58 is formed. The fan body 41 includes the head provided with a hemispherical curvature 42 to the neck 45 followed. The neck has at its end opposite the head designed as a ring carrier 46 which extends laterally over the mantle of the Fächerkörpers protruding stretches, and by webs 52 communicating with the neck ( 2a ). The carrier 46 has a radially extending inlet opening 47 for the polymer melt from the extruder 30 on, with the inlet opening 47 in one in the fan body 41 arranged centric along the central longitudinal axis 59 the fan body extending channel 48 empties. The channel 48 extends to the area of the head 42 , Radially outgoing from the channel are circumferentially distributed at the neck before the transition to the head outlet openings 49 provided, with each outlet opening 49 for the polymer melt, a tangential on the lateral surface of the fan body 41 extending, towards the head oriented groove 50 having. The annular carrier 46 has a radial distance to the fan body 41 on. The connection between the annular support 46 and fan bodies 41 done by at least one bridge 52 , The radial distance between the fan body and the carrier 46 is through a kind of pinhole 53 covered, the several openings 51 for the passage of a fiber strand 5 in the annulus 54 on the side of the neck of the fan body 41 has over.

With 56 designated hood has the central opening 57 on, with the centric opening in alignment with the central longitudinal axis 59 of the fan body 41 lies. That means that the centric opening 57 the dome over the vertex of the hemispherical head 42 located.

The feeding of the individual fiber strands 5 takes place, as already stated by the individual openings 51 , In the area of the transition from the neck 45 to the head 42 characterized by the broken line 44 , the fanning of the fiber strand takes place in the individual filaments forming the fiber strand. The fanning out is roughly diamond-shaped in plan view. In this area are also the outlet openings 49 for the polymer melt with the adjoining tangential grooves 50 , In particular in this area, ie the area of spreading or fanning of the fiber strand into individual filaments, the impregnation takes place. Due to the tangential grooves, which are in each case at the outlet openings 49 connect, the polymer melt receives a twist in the direction of the grooves, ie also in the direction of the head 42 to, which leads to a swirling of the melt in this area, with the result that intensive wetting of the individual filaments takes place. The individual fiber strands 5 are then together as a prepreg strand 55 out of the opening 57 guided in the hood, which then through the nozzle 60 is compressed.

This prepreg strand 55 will then in the 3 and 3a shown tempering 70 fed. The tempering device 70 includes two counter-rotating rollers 71 . 72 , where the role 72 a circumferential groove 72a and the role 71 Corresponding thereto, a circumferential spring 71a having. Tongue and groove, as this is in the view of 3 and 3a results in one another, being in the groove 72a the prepreg strand is guided. By choosing the appropriate size of the groove 72a and corresponding to the circulating spring 71a Both compression and shaping of the prepreg strand may take place. In addition, the roles serve as part of the tempering 70 either the cooling or heating of the prepreg strand, as desired. In particular, cooling of the rollers provides for faster cooling of the prepreg strand and reduction in the thermal loading of the fibers, which is essential when using cellulose or natural fibers, in conjunction with a higher melting temperature polymer.

A method in which cut fiber strand sections are fed directly to an extruder is in 4 shown. Here again is a bobbin holder 10 provided with several coils 11 , From the coils 11 each becomes a fiber strand 5 through a conveyor unit 100 subtracted, with the conveyor unit 100 appears as a counter-rotating pair of rollers, between which the individual fiber strands 5 separately a cutting tool 110 be supplied. Between the coil holder 10 and the conveyor unit 100 can be a drying device 20 be provided as it has already been described. The cutting tool 110 results schematically from the illustration according to 5 , According to 5 is a movable knife 111 provided that on a cutting block 112 under shearing of the fiber strand 5 along slides. Depending on the length of the cut fiber strand section results for the cut section a shape that is approximately in accordance with 6 equivalent. It can be seen here that the fiber strand section is spread or fanned out by the shearing cut into individual fibers or filaments. This certainly has advantages if the individual fiber strand sections spread in this way are located in the extruder 120 over the funnel 121 be supplied. Into the funnel is about the metering device 130 also added the polymer, for example in the form of granules. From the extruder 120 becomes an extrusion strand 55a discharged, which consists of a thermoplastic polymer embedded homogeneously or evenly distributed having the individual filaments of the fiber strand sections. The one with 55a designated extrusion line is also characterized by a feature of this method in 4 With 70 designated tempering fed. The tempering device 70 includes two counter-rotating rollers 71 . 72 , where the role 72 a circumferential groove 72a and the role 71 Corresponding thereto, a circumferential spring 71a having. Tongue and groove, as this is in the view of 3 and 3a results in one another, being in the groove 72a the extrusion strand 55a is guided. By choosing the appropriate size of the groove 72a and corresponding to the circulating spring 71a Both compression and shaping of the extrusion strand can take place. In addition, the roles serve as part of the tempering 70 the temperature, in particular the cooling of the extrusion strand. In particular, cooling of the rolls provides for faster cooling of the extrusion strand and reduction of thermal stress on the fibers, which is essential when using cellulose or natural fibers in conjunction with a higher melting temperature polymer.

Downstream of the tempering is a with 80 designated strip, as well as the Granuliereinrichtung 90 for the production of the compound granules.

For even better mixing or wetting of the individual fibers of the prepreg strand 55 or the extrusion strand 55a can take care of the strand 55 . 55a immediately after leaving the extrusion die 40 or the extruder 120 be redirected several times. For this purpose, the device is used 150 according to the schematic representation in 7 , The deflection device 150 comprises several, in particular rotatable rollers or rollers 155 , which are offset from one another, wherein by the deflection of the strand kneading of the strand takes place, with the result, the degree of wetting of the fibers with the polymer is further increased. The deflection takes place meandering, in addition, a lateral deflection can be made.

Claims (5)

Extrusion tool ( 40 ) for fanning out at least one fiber strand ( 5 ) and for impregnating the fiber strand ( 5 ) with a polymer melt, wherein the extrusion tool a fan body ( 41 ) as well as the fan body ( 41 ) surrounding hood ( 56 ), wherein the hood has a central opening ( 57 ) for the at least one fiber strand ( 5 ), wherein the at least one fiber strand ( 5 ) on the side of the fan body ( 41 ) to the opening in the hood ( 56 ), fanning the at least one fiber strand ( 5 ) on the fan body ( 41 ), wherein the fan body ( 41 ) in the area of the fanning out of the at least one fiber strand ( 5 ) at least one outlet opening ( 49 ) for the polymer melt, characterized in that the fan body ( 41 ) a head provided with a hemispherical curvature ( 42 ), wherein the head ( 42 ) a neck ( 45 ), wherein the neck ( 45 ) forming at least one opening ( 51 ) for at least one fiber strand ( 5 ) with a carrier ( 46 ) and wherein the neck ( 45 ) in the area of the transition to the head ( 42 ) the at least one outlet opening ( 49 ) for the polymer melt. Extrusion tool according to claim 1, characterized in that the carrier ( 46 ) is designed as a ring carrier. Extrusion tool according to one of the preceding claims 1 or 2, characterized in that at the outlet opening ( 49 ) a tangential in the direction of the head ( 42 ) leaking groove ( 50 ). Extrusion tool according to one of the preceding claims, characterized in that the carrier ( 46 ) a radially in the fan body ( 41 ) extending inlet opening ( 47 ) for the polymer melt passing through a channel ( 48 ) in the fan body ( 41 ) with the at least one outlet opening ( 49 ) for the polymer melt. Extrusion tool according to one of the preceding claims, characterized in that the carrier ( 46 ) as ring bearer the fan body ( 41 ) spaced to form one, but preferably a plurality of circumferentially distributed openings ( 51 ) for a corresponding plurality of fiber strands ( 5 ), whereby the shark ( 45 ) circumferentially distributed in the area of the transition to the head ( 42 ) a plurality of outlet openings ( 49 ) for the polymer melt.

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